1. Field of Invention
The present invention relates more particularly to a vehicle headlamp system, and more generally to a projector-type vehicle headlamp system that does not use a shade interposed between a light source and a lens.
2. Description of Related Art
With developments of optical systems relevant to vehicle headlamp systems, many headlamp systems have been designed, such as the multi reflector (MR) vehicle headlamp system, the free-form reflector (FR) vehicle headlamp system, and the poly-ellipsoid system (PES) vehicle headlamp system. The PES vehicle headlamp system is a projector-type headlamp system that has more advantages than the other systems.
Firstly, the headlamp height on the PES vehicle headlamp system may be easily adjusted to adapt to the road conditions. Easy headlamp height adjustment increases overall driving safety.
Secondly, the headlamp light pattern cut-off line of the PES vehicle headlamp system is clearer than the cut-off lines of the other vehicle headlamp systems. The passing beam generated is therefore more comfortable and safer to the drivers who come from the front.
FIG. 1 shows the testing zones of a light pattern for a passing light beam from a conventional vehicle headlamp system that conforms to the passing-beam requirements of the ECE (Economic Commission for Europe) regulations. In FIG. 1, character “v” indicates a vertical plane and character “h” indicates a horizontal plane. The brightest testing point (75R) of the bright testing zone is adjacent to the dark testing zone (such as Zone III). The required illumination of the brightest testing point (75R) is equal to or more than 12 lux, and the required illumination of the dark testing zone (such as Zone III) is equal to or less than 0.7 lux. The required illumination of the light pattern between the bright and dark testing zones changes sharply that makes it difficult to design a vehicle headlamp with a desirable light pattern. Moreover, the required illumination of a light pattern needs to produce a clear cut-off line to divide the bright and dark testing zones.
FIG. 2-FIG. 4 illustrate a conventional PES vehicle headlamp system 100, comprising an ellipsoidal reflector 110, a light source (a bulb or a filament) 120, a lens 130 and a shade 140. The ellipsoidal reflector 110 focuses the light rays emitted from the light source 120 located at the first focal point 111 of the ellipsoidal reflector 110 into a second focal point 112. The lens 130 then moves to make sure that its focal point 131 (The focal point 131, which is a third focal point 131 of the conventional PES vehicle headlamp system 100, is one focal point of the lens 130.) overlaps the second focal point 112 of the ellipsoidal reflector 110. Thereafter, the shade 140 is interposed between the ellipsoidal reflector 110 and the lens 130 to block some of the light rays emitted from the ellipsoidal reflector 110 and the light source 120 in order to produce a desirable light pattern with a clear cut-off line.
Although the shade 140 enables the conventional PES vehicle headlamp system 100 to generate a desirable light pattern by blocking some of the light rays, it lowers the utility rate of the light rays emitted from the light source. Generally, about half of the light rays emitted from the light source will be blocked by the shade 140, reducing the light source lighting efficiency by half.
FIG. 5A shows an image of the light patterns for lighting distribution zones of a conventional PES vehicle headlamp system 100 that does not use a shade 140. The lighting distribution zones are divided into six lighting distribution zones. These six lighting distribution zones are lighting distribution zone i, zone ii, zone iii, zone iv, zone v, and zone vi. FIG. 5B shows the six reflecting zones on an ellipsoidal reflector 110 that separately corresponded to the six lighting distribution zones. These six reflecting zones are reflecting zone i′, zone ii′, zone iii′, zone iv′, zone v′ and zone vi′, which respectively corresponds to the lighting distribution zone i, zone ii, zone iii, zone iv, zone v and zone vi.
FIG. 6 is an lighting distribution of the glare light produced in lighting distribution zone vi of a conventional PES vehicle headlamp system 100 that does not use a shade 140, and in which reflecting zone vi′ of the reflector ellipsoidal 110 totally redirects the light rays emitted from the light source 120 to lighting distribution zone vi. Because the light source 120 is positioned at the first focal point 111, the light rays emitted from the light source 120 via the reflecting zone vi′ form lighting distribution zone vi, which is mostly spread above the Y=0 horizontal line in FIG. 6 indicating that serious glare light is generated. The glare light compromises the safety of passing drivers. Therefore, the shade 140, which is used to prevent the occurrence of glare light, is one of the essential elements of a conventional PES vehicle headlamp system 100 but the shade 140 reduces the illuminating utility rate of the light source 120.
Additionally, in a conventional PES vehicle headlamp system 100 that does not use a shade 140, the lighting distribution spread is lowered below the Y=0 horizontal line (a desirable light pattern) by combining the ellipsoidal reflector 110 with two or more reflectors that have reflecting surfaces usually designed with an ellipsoid equation to ensure that the focal point of each reflector is located at the same point. Typically, the ellipsoidal reflector 110 of the conventional PES vehicle headlamp system 100 that does not use a shade 140 is composed of plural reflectors that generate the desirable light pattern. But the junctions (crevices) of the plural reflectors usually form one or more steps, which are the junction (crevice) of two or more different level surfaces of the plural of reflectors, also cause glare light.
For the foregoing reasons, there is a need to improve the illuminating utility rate of the light source without compromising the light pattern of the vehicle headlamp.